1. Field of the Invention
The present invention relates to a travel-driving mechanism for a self-propelled working machine such as a lawn mower, which travels by using power of a driving source.
2. Description of the Related Art
A self-propelled working machine such as a lawn mower, which travels by using power of a driving source is a working machine, which is moved by pushing or pulling by the operator and is turned to change the direction thereof after the travel of the working machine by the driving source is stopped. A clutch is provided in a unit for transmitting travel power. When the operator moves the working machine, the clutch is disengaged to make easy the pushing or pulling by the operator.
A clutch mechanism, which is disengaged irrespective of the direction of power transmission, should have an actuator for allowing the clutch to be engaged or disengaged. The actuator increases the manufacturing cost of the clutch mechanism. For this reason, a simple one-way or one-directional clutch has been generally used (for example, refer to JP-UM-B-62-2338).
In the case of the one-way or one-directional clutch, when the working machine stops after travel by a driving source, the one-directional clutch is in the engaged state. Thus, when the working machine is to be pulled rearward, the driving shaft of the driving source rotates due to the backward rotation of the driving wheels in the engaged state of the clutch. For this reason, the operator must move the working machine under the large load. Thus, disengaging operation of the clutch needs to be performed to solve the problem.
A machine having a two-way or bi-directional clutch has been proposed, which is provided with a unit for transmitting travel power (refer to JP-A-2005-127448).
The two-way or bi-directional clutch is a clutch in which only forward directional power of the driving shaft of the driving source is transmitted to the driving wheels and the forward and backward torque of the driving wheels is not transmitted to the driving shaft if the clutch is not engaged.
In the case of the bi-directional clutch, when a machine stops after travel by a driving source, the driving wheels are disconnected from the driving shaft and are free if the clutch is not engaged. Accordingly, it is possible for the operator to easily move the working machine forward and backward. However, when the machine stops after travel by the driving source, the driving shaft stops but the driving wheels rotate due to inertia and the torque of the driving wheels causes the driving shaft to rotate without disengagement of the clutch. In this case, when the working machine is pulled rearward after the stop, it is difficult for the operator to move the machine under the large load caused by the engaged state of the clutch.